Main menu

Post navigation

The Evincehackfest took place last week from 23rd to 25th July in Strasbourg. Yes, 3 days only, but very productive in my opinion, I’ll summarize all the cool stuff we worked on.

HiDPI

This work was initially started by Owen, and then Germán kept the patches up to date with evince git master. I reviewed all the pending patches and updated the thumbnails one and the result is that evince doesn’t look blurry on HiDPI screens any more.

Evince running with GDK_SCALE=2

Recent View

This was a GSoC project of 2013, but the patch provided by the student was never in an “upstreamable” state. Again Germán, who always loved this feature, took care of the patch addressing my review comments. At the beginning of the hackfest most of the work has already been done, we only needed a few more review iterations during the hackfest to finally push this feature to master. The idea is to show the list of recent documents as an icon view with thumbnails and documents metadata. This view is loaded when evince is launched without any document replacing the useless empty window we had before. It also replaces the recent documents submenu in the gear menu.

UI improvements

The move to the header bar recently made the toolbar look a bit cluttered, mainly because the title might use a lot of space. We discussed several ideas to improve the header bar and implemented some of them:

Annotations

Giselle and Anuj, our GSoc students this year, worked on their projects to improve the annotations support in both Evince and poppler.

Anuj wrote some patches to add support for Free Text annotations to poppler glib API. After a couple of review iterations and discussions about the API, the patches are now in bugzilla waiting for a final review (I hope to find the time soon)

Comics backend

Juanjo Marín focused on the comics backend, working on a patch to use libarchive to uncompress the documents instead of spawning external command line tools.

Gestures

I started to review the gestures branch during the hackfest, patches looked clean and simple, but since I was not familiarized with the new GTK+ touch API and I didn’t have a touch screen to try it out either, I decided to wait after the hackfest and see it in action in garnacho’s laptop during GUADEC. Carlos explained to me how the touch API works in GTK+ and I could check it actually works great. The code doesn’t affect the normal use with the mouse, so the branch will be merged in master soon.

And of course not everything was hacking

THANKS!

Many thanks to Alexandre Franke for the local organization, everything worked perfectly. Of course thanks to the GNOME Foundation for sponsoring the GSoC students, Giselle and Anuj, and Igalia for sponsoring all the Igalians attending the hackfest. Thanks also to Epitech for allowing us to do the hackfest there before the GUADEC.

DOM touch events support

WebKitWebView now processes the touch events happening in the widget to notify the DOM, making modern websites using DOM touch API properly work. Carlos Garnacho has taken a screencast to show it in action

Plugins cache

When the first page containing plugins was loaded, the UI process got blocked for some time, while the plugins were scanned. This was one of the most annoying bugs of WebKitGTK+ introduced in 2.0. Plugins are synchronously scanned on demand during the page load, and it’s something that can’t be avoided. WebKitGTK+ 2.4 uses a persistent cache to store information about all plugins, so that plugins are only scanned the first time or when they change.

WebKit1 deprecation

There’s one last thing I would like to mention. Even when WebKit1 API has been deprecated since we released WebKitGTK+ 2.0, we have kept shipping both APIs in our tarball releases. A decision hasn’t been made yet, but this is probably the last release including the WebKit1 API, we have plans to remove the WebKit1 code from trunk and move all the build bots to run only WebKit2 tests. We encourage everybody to port their applications to WebKit2, submitting bug reports if there’s anything preventing the switch, and of course we are happy to help on IRC, mailing list, etc.

As every year many ideas came up during the WebKitGTK+ hackfest presentation, but this time there was one we all were very excited about, the multiple web processes support. Apple developers already implemented the support for multiple web processes in WebKit, which is mostly cross platform, but it requires the network process support to properly work (we need a common network process where cookies, HTTP cache, etc are shared for all web processes in the same web context). Soup based WebKit ports don’t implement the network process yet, so the goal of the hackfest became to complete the network process implementation previously started by EFL and Nix guys, as a first step to enable the multiple web processes support. Around 10 people were working on this goal during the whole hackfest, meeting from time to time to track the status of the tasks and assigning new ones.

Andy updated some of the patches already waiting for a review and set up github repo with all those patches so that we all could work without dealing with individual patches.

Sergio updated the patch proposed by Balazs to implement the bits required to connect the network process with the web process using UNIX domain sockets.

After all this awesome work we managed to have the basic support, with MiniBrowser perfectly rendering pages and allowing navigation using the network process. But as expected, there were some bugs and missing features, so I ran the WebKit2 unit tests and we took failing tests to investigate why they were failing and how to fix them.

Adrian submitted a patch to add new API to select the process model that will be used when the network process support is finished. He is also working on the problems of having multiple instances of the web extensions.

So, we are actually far from having a complete and stable network process support, but it’s a huge step forward. The good news is that once we have network process implemented, the multiple web processes support will work automatically just by selecting the multiple web process model.

All this sounds like a lot of work done, but that’s only a small part of what has happened this week in Coruña:

Martin and Gustavo made moreparts of WebKit actually build with the cmake build.

And I’m sure I’m missing more great stuff done that I could not follow closely. It’s definitely been a very productive hackfest that it would haven’t been possible without the sponsors, Igalia and the GNOME Foundation. Thanks!

New Web Inspector

WebKitGTK+ now uses the new Web Inspector recently opensourced and upstreamed by Apple. We took advantage of the migration to improve the way inspector resources are distributed by compiling them in the WebKitGTK+ library as GResources. This means that resources are now always available without having to run make install or set environment variables.

Initial Wayland support

WebKitGTK+ 2.2 can be built with Wayland target if it’s available (it requires GTK+ 3.10 compiled with Wayland support). Not everything is fully supported yet, but the WebKit layout tests can be run under the Weston compositor and WebGL content works under Wayland displays too. There’s more detailed information in Žan Doberšek’s blog.

Video accelerated compositing support

When accelerated compositing is enabled, the GStreamer media player can play videos using OpenGL. You can find more details in Víctor’s blog.

Custom JavaScript injection

This was one of the major regressions in WebKit2GTK+ compared to the WebKit1 API. WebKitGTK+ 2.2 now allows to inject custom JavaScript code using the JavaScriptCore C API from a WebKit Web Process Extension. New API has been added to also allow running specific JavaScript code in isolated worlds. You can find examples about how to use this API and how to write Web Process Extensions in general in this post.

Improved accessibility support in WebKit2

Accessibility support in WebKit2 has been reworked to not depend on pango and gail, which resulted in several bugs fixed and a much better accessibility support. Check Mario’s blog for all the details.

The multiprocess architecture of WebKit2 brought us a lot of advantages, but it also introduced important challenges, like how to expose some features that now live in the Web Process (DOM, JavaScript, etc.). The UI process API is fully asynchronous to make sure the UI is never blocked, but some APIs like the DOM bindings are synchronous by design. To expose those features that live in the Web Process, WebKit2GTK+ provides a Web Extensions mechanism. A Web Extension is like a plugin for the Web Process, that is loaded at start up, similar to a GTK module or gio extension, but that runs in the Web Process. WebKit2GTK+ exposes a simple low level API that at the moment provides access to three main features:

GObject DOM bindings: The exactly same API used in WebKit1 is available in WebKit2.

WebKitWebPage::send-request signal: It allows to change any request before it is sent to the server, or even simply prevent it from being sent.

Custom JavaScript injection: It provides a signal, equivalent to WebKitWebView::window-object-cleared in WebKit1, to inject custom JavaScript using the JavaScriptCore API. (Since 2.2)

This simple API doesn’t provide any way of communication with the UI Process, so that the user can use any IPC mechanism without interfering with the internal WebKit IPC traffic. Epiphany currently installs a Web Extension to implement some of its features such us pre-filled forms, ads blocker or Do Not Track using D-BUS for the communication between the Web Extension and the UI Process.

How to write a Web Extension?

Web Extensions are shared libraries loaded at run time by the Web Process, so they don’t have a main function, but they have an entry point called by the WebProcess right after the extension is loaded. The initialization function must be called webkit_web_extension_initialize() and it receives a WebKitWebExtension object as parameter. It should also be public, so make sure to use the G_MODULE_EXPORT macro. This is the function to initialize the Web Extension and can be used, for example, to be notified when a web page is created.

The extension will be installed in $(libdir)/MyApp/web-extension so we need to tell WebKit where to find web extensions before the Web Process is spawned. Call webkit_web_context_set_web_extensions_directory() as soon as possible in your application, before any other WebKit call to make sure it’s called before a Web Process is launched. You can create a preprocessor macro in the Makefile.am to pass the value of the Web Extensions directory.

This should be enough. You should be able to build and install the Web Extension with you program and see the printf message every time a page is created. But that’s a useless example, let’s see how to use the Web Extensions API to do something useful.

Accessing the DOM

The GObject DOM bindings API available in WebKit1 is also exposed in WebKit2 from the Web Extensions API. We only need to call webkit_web_page_get_dom_document() to get the WebKitDOMDocument of the given web page.

Using WebKitWebPage::send-request signal

Using the Web Extensions API it’s possible to modify the request of any resource before it’s sent to the server, adding HTTP headers or modifying the URI. You can also make WebKit ignore a request, for example to block resources depending on the URI, by simply connecting to the signal and returning TRUE.

Extending JavaScript

Using the JavaScriptCore API it’s possible to inject custom JavaScript code by connecting to the window-object-cleared signal of the default WebKitScriptWorld. You can get the global JavaScript execution context by calling webkit_frame_get_javascript_context_for_script_world() for the WebKitFrame passed as parameter of the window-object-cleared signal.

But what’s so special about WebKitGTK+ 2.0?

The WebKit2GTK+ API is now the default one. This means that it’s now considered stable from the API/ABI backwards compatibility point of view, and that the old WebKit1 API is in maintenance mode and kind of deprecated. We will maintain both APIs, but we don’t plan to work on WebKi1 other than fixing bugs.

We encourage everybody to port their existing WebKitGTK+ applications to WebKit2, although we know the WebKit2 GTK+ API is not ready for all applications yet. We will work on adding new API during next release cycle, so let us know if you are missing some API that prevents you from porting your project.

What are the benefits of the WebKit2 GTK+ API?

We have talked several times about the advantages of the multi-process architecture of WebKit2, robustness, responsiveness, security, etc. All of the details of the multi-process separation are mostly transparent for the API users, bringing all those benefits for free to any application using WebKit2 GTK+. We have developed the API on top of this multi-process architecture, but also with the experience of several years developing and maintaining the WebKit1 GTK+ API, learning from the mistakes made in the past and keeping the good ideas. As a result, the WebKit2 API is very similar to the WebKi1 in some parts and quite different in others. We started from scratch with the following goals:

Simple and easy to use. Instead of porting the WebKit1 API to WebKit2, we decided to add new API on demand. We set some milestones based on porting real applications, adding new API required to port them. This also allowed us to design the API, not only thinking about what we want or need to expose, but also how the applications expect to use the API.

Consistency. We have tried hard to be consistent with the names of the functions, signals and properties exposed by the API.

Flexibility. When possible, the API allows to use your own implementation of some parts that can be adopted to different platforms. So, you can use your own file chooser, JavaScript dialogs, context menu, print dialog, etc.

It works by default. For all those features where a custom implementation can be used, there’s a default implementation in WebKit that just works by default.

Unit tests. We have enforced all new patches adding API to WebKit2 GTK+ to include also unit tests, so the whole API is covered by unit tests.

Let’s see the major changes and advantages of this new WebKi2 API.

WebKitWebView is a scrolling widget

For API users this means that WebKitWebView should not be added to a GtkScrolledWindow, the widget is scrollable by itself. Actually this is also the case of the WebKitWebView in WebKit1, but some hacks were introduced to allow the widget to be used inside a GtkScrolledWindow. This caused a lot of headaches due to the synchronization between the internal scrolling and the GTK+ scroll adjustments. So now the main scrollbars are also handled by the WebKitWebView which, among other things, fixed the problem of the double scrollbars in some web sites.

Embedded HTTP authentication dialog

The default implementation of the HTTP authentication embeds a dialog in the WebView instead of using a real GtkDialog. It’s also integrated with the keyring by default using libsecret.

GTK+ 2 plugins (flash)

Plugins also run in a different process that is built with GTK+ 2 to support the most popular plugins like flash that still use GTK+ 2.

Web Inspector

The Web Inspector works automatically in both docked and undocked states without requiring any API call.

It also has support for remote inspecting.

Accelerated compositing

Accelerated compositing is always enabled in WebKit2.

Future plans

During the next release cycle we’ll work on fixing bugs and completing the API, see our RoadMap for further details, but we’ll also explore some other areas not directly related the the API:

I also took advantage of the hackfest time, to re-take a task I had pending for some time, adding an API to WebKit2 to handle SSL errors. I didn’t have time to finish the API, but managed to write a first patch to set a policy for SSL errors. For now it only allows to ignore SSL errors and continue the load or make the load fail in case of SSL errors. The idea is to add a new policy to ask the user what to do.

Even though it was not part of my initial plans for the hackfest I ended up working on the document reading integration in Epiphany. I wrote an initial patch for Epiphany to load documents supported by Evince embedded in the window like a web view. There are still a lot of features to integrate like zooming, searching, printing, etc.

Epiphany showing a PDF document

I set a milestone to switch Epiphany to WebKit2 by default at the end of the hackfest, but I didn’t have time to fix all the regressions. We are a lot closer, though.

Since the Epiphany migration to WebKit, websites with an invalid SSL certificate were marked as untrusted with the unsecure lock icon in the location bar. However, it wasn’t possible to know what was wrong with the certificate nor the certificate details. Using the certificate viewer widget available in gcr, I’ve implemented a dialog to show information about the possible SSL errors and certificate details in Epiphany. This also means Epiphany now depends on gcr.

During the last week, the Igalia WebKit team has been working on adding the initial support for WebKit2 into Epiphany git master. As we did for Devhelp, there’s a configure option (–with-webkit2) that can be used to build Epiphany with WebKit2. The option is disabled by default for now. The WebKit2 GTK+ API is more and more mature and complete, but there are still some important features to implement in order to be able to enable WebKit2 by default in Epiphany. Nevertheless, the main functionality works already and we encourage everybody to give it a try and provide feedback and bug reports. You can also take a look at the Epiphany metabug or the WebKit2 GTK+ API roadmap if you want to help.

Epiphany with WebKit2 playing a random Flash video

The plan is still to have a first stable version of WebKit2 GTK+ API for GNOME 3.6, but Epiphany will switch to WebKit2 by default when we manage to fix all the regressions, hopefully for GNOME 3.8.

The GNOME Project has released GNOME 3.4, the second major release of GNOME 3. A lot of new features, UI improvements and other enhancements are included in this release, as well as important changes in the development platform. You can see all the details in the release notes.

One of the applications that has received a major revamp is Epiphany, the GNOME Web Browser, not only because of the beautiful new interface, but it also has significant improvements in performance and stability. If Epiphany is not your default browser, give it a try when you upgrade to GNOME 3.4. See Xan‘s and Diego‘s blog posts for more details of the new Web Browser.

WebKit2

GNOME 3.4 includes WebKitGTK+ 1.8.0, the first stable release that contains an initial WebKit2 GTK+ API. It’s disabled by default, though, since it’s still a preliminary version, so you need to build with –enable-webkit2 configure option. It’s already possible to try it out with Devhelp 3.4 which can be optionally built with WebKit2 using –with-webkit2 configure option. If the current API is enough to port your application, give it a try and let us know, you can use the webkit2 devhelp branch as a reference. We’ll provide a migration guide soon too.